As with Sword and Shield, you will be able to claim these bonuses in Pokemon Legends: Arceus if you launch the game as a user with play records either Eevee or Pikachu.
The Pokemon Company is handing out an incentive to those who’ve played recent Pokemon titles and who pick up Pokemon Legends: Arceus.
If you have play records from Pokemon: Let’s Go Eevee or Pikachu, you’ll be able to claim a Pikachu Mask and an Eevee Mask in Pokemon Legends: Arceus.
To claim these bonuses, you will need to launch Pokemon Legends: Arceus as a user with play records from Sword or Shield on your Switch system.